• Computers and Concrete
• /
• v.13 no.1
• /
• pp.49-70
• /
• 2014

Steel fiber-reinforced concrete (SFRC) is known as one of the efficient modern composites that can greatly enhance the material performance of cracked concrete in tension. Such improved tensile resistance mechanism at crack interfaces in SFRC members can be heavily influenced by methodologies of treatments of crack direction. While most existing studies have focused on developing the numerical analysis model with the rotating-angle theory, there are only few studies on finite element analysis models with the fixed-angle model approach. According to many existing experimental studies, the direction of principal stress rotated after the formation of initial fixed-cracks, but it was also observed that new cracks with completely different angles relative to the initial crack direction very rarely occurred. Therefore, this study introduced the direct tension force transfer model (DTFTM), in which tensile resistance of the fibers at the crack interface can be easily estimated, to the nonlinear finite element analysis algorithm with the fixed-angle theory, and the proposed model was also verified by comparing the analysis results to the SFRC shear panel test results. The secant modulus method adopted in this study for iterative calculations in nonlinear finite element analysis showed highly stable and fast convergence capability when it was applied to the fixed-angle theory. The deviation angle between the principal stress direction and the fixed-crack direction significantly increased as the tensile stresses in the steel fibers at crack interfaces increased, which implies that the deviation angle is very important in the estimation of the shear behavior of SFRC members.

• The Korean Journal of Applied Statistics
• /
• v.32 no.5
• /
• pp.703-720
• /
• 2019

The influence of temperature on electricity demand is increasing due to extreme weather and climate change, and the climate impacts involves nonlinearity, asymmetry and complexity. Considering changes in government energy policy and the development of the fourth industrial revolution, it is important to assess the climate effect more accurately for stable management of electricity supply and demand. This study aims to analyze the effect of temperature change on electricity demand using the partial linear model. The main results obtained using the time-unit high frequency data for meteorological variables and electricity consumption are as follows. Estimation results show that the relationship between temperature change and electricity demand involves complexity, nonlinearity and asymmetry, which reflects the nonlinear effect of extreme weather. The prediction accuracy of in-sample and out-of-sample electricity forecasting using the partial linear model evidences better predictive accuracy than the conventional model based on the heating and cooling degree days. Diebold-Mariano test confirms significance of the predictive accuracy of the partial linear model.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.1190-1200
• /
• 2010

A method was developed to determine resilient modulus for crushed rock-soil mixtures whose usage has been increased recently without engineering specifications. The method is based on the subtle different modulus called nonlinear dynamic modulus and was lately implemented in residual soils and engineered crushed-stones. Hereby. the same method was expanded to crushed rock-soil mixtures containing as large grain diameter as 300mm. The method utilize field direct-arival tests for the determination of maximum Young's modulus, and a large scale free-free resonant column test, which is recently developed to is capable to test as large grain diameter as 25mm, for modulus reduction curves. The prediction model of resilient modulus was evaluated for crushed rock-soil mixtures of a highway construction site at Gimcheon, Korea.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.5
• /
• pp.37-46
• /
• 2007

This is the second of two companion papers that describe non-prismatic beam element for nonlinear seismic analysis of steel moment frames. Described in a companion paper is the formulation of a non-prismatic beam element to model the elastic and inelastic behavior of steel beams, which have reduced beam sections(RBS). This study describes the determination of yield surfaces, stiffness parameters, and hardening (or softening) rule parameters for RBS beam element. Analytical results of the RBS beam element show good correlation with test data and Finite Element Method(FEM) results.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.4
• /
• pp.1-7
• /
• 2005

In vehicle door system, weatherstrip seals protect passengers form noise, dust, rain and wind out of the vehicle. The higher efficient a weatherstrip is, the more durable it is in contact between the door and body frame. In this study, nonlinear finite element(FE) analysis is performed to obtain cauchy-stresses, displacements and reaction forces of the weatherstrip. Mechanical properties of the weatherstrip is obtained by uniaxial tension test. The MARC which is a commercial software for the nonlinear analysis of a flexible FE model is used. Twenty-one cases of the FE model are developed by using Ogden-foam formulation. In the results of nonlinear FE analysis, the most valuable deformation of the weatherstrip occurred when displacement control value reaches 7.2mm. Severe deformation is observed as the displacement control value become more increased. When the weatherstrip is designed, it would be considered that the displacement value of the weatherstrip has to be less than 7.2mm.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.04a
• /
• pp.341-348
• /
• 2000

The existing solid circular RC pier without seismic detailing is found to have poor ductility due to the premature bond failure of lap spliced longitudinal bars. The steel-jacket was introduced to prevent this unexpected type of failure. The nonlinear behavior and he seismic performance of the retrofitted pier were examined through the scale model test and compared with those of existing one. It is confirmed from the test results that the steel-jacket retrofitting can be used as an measure to improve seismic performance considerably.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.147-150
• /
• 1996

This paper describes controller design and implementation method for controlling the temperature distribution in a thermal stratified wind tunnel(TSWT) by using a neural network algorithm. It is impossible to derive a mathematical model of the relation between heat inputs and temperature outputs in the test section of the TSWT governed by a nonlinear turbulent flow. Thus inverse neural network models with a multi layer perceptron structure are used in a feedforward control loop and feedback control loop to generate an arbitrary temperature distribution in the test section of the TSWT.

• Journal of Institute of Control, Robotics and Systems
• /
• v.4 no.5
• /
• pp.666-673
• /
• 1998

To increase reliability and performance of an IMS(Intelligent Manufacturing System), fault tolerant control based on an accurate fault diagnosis is needed. In this paper, robot FDI(fault detection and identification) is proposed for IMS where the robot is controlled with state estimates of a nonlinear filter using a mathematical robot model. The Chi-square test and GLR(General likelihood ratio) test are applied for fault detection and fault size is estimated by a proposed bias filter. Performance of the proposed algorithm is tested by simulation for studies.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.9
• /
• pp.25-36
• /
• 2011

The behavior of the dry-stone masonry retaining structure has been investigated via physical model test and numerical simulation. In the model test, the digital image analysis using PIV technique was employed to measure horizontal displacements in the backfill soils and retaining blocks. For finite element numerical analyses, the commercial code, ABAQUS, was used. The horizontal displacements observed in the model test showed that the development of the failure surface is progressive. Numerical results showed that in most cases horizontal earth pressure is distributed similarly to a conventional Rankine’s distribution. However, lower values of the internal friction angle of the backfill soils and interface friction angle in the front blocks produce irregularly nonlinear distribution of the horizontal earth pressure.

• Geomechanics and Engineering
• /
• v.9 no.5
• /
• pp.585-599
• /
• 2015

Laboratory model tests were conducted to investigate the effect of surcharge loading rate on the magnitude of lateral displacement of prefabricated vertical drains (PVDs) improved deposit. The test results indicate that under the condition that the system had sufficient factor of safety (FS) ($FS{\geq}1.2$), for the similar model ground under the same total applied surcharge load, the lateral displacement increases with the increase of loading rate. The test results have been used to check the validity of a previously proposed method for predicting the maximum lateral displacement, and it shows that the data points are around the middle line of the predicted range, which supports the usefulness of the proposed method. The basic idea of the prediction method is an empirical relationship between the normalized lateral displacement (NLD) and a ration of load to the undrained shear strength of the deposit (RLS). The model test results offer some modifications of the NLD-RLS relationship: (1) instead of a bilinear relationship, NLD-RLS relationship may be entirely nonlinear; (2) the upper bound value of RLS for the proposed method can be used may be limited to 2.1 instead of the originally proposed value of 3.0.